Administration of an Immune Stimulant during the Transition Period Improved Lipid Metabolism and Rumination without Affecting Inflammatory Status

SIMPLE SUMMARY: Immune stimulants are widely used to address immune dysfunctions that occur in transitioning dairy cows, reducing the likelihood they will develop infectious diseases. This study elucidates the effectiveness of an immune stimulant in promoting rumination recovery, reducing lipid mobilization and ketogenesis, and affecting the levels of circulating antioxidant systems in early lactation. These findings highlight the stimulant’s potential effect in treating metabolic disorders of the transition period in dairy cows. ABSTRACT: Omnigen-AF (OAF) increases leukocyte functions in immunosuppressed animal models and reduces incidence of infectious diseases in early lactating dairy cows, although its mode of action is still unclear. This study aims to provide a wider perspective of the metabolic effect of OAF to test its potential as a strategy to address metabolic disorders of the transition period. A group of 10 Holstein dairy cows were divided into 2 groups: The treated group (IMS; 5 cows) received 32.5 g of OAF twice a day (65 g d(−1)) as top-dress in the morning and afternoon feeds from −55 to 42 days from calving (DFC), whereas the control group (CTR; 5 cows) received no supplementation. From −62 to 42 DFC, body condition score, body weight, dry matter intake, rumination time and milk yield were measured; blood samples were collected weekly to assess a wide hematochemical profile and to test white blood cell functions by ex-vivo challenge assays. At 30 DFC, rumen fluid was collected and analyzed for pH, volatile fatty acids composition, urea nitrogen, and lactate contents. Data were submitted to ANOVA using a mixed model for repeated measures, including treatment, time, and their interaction as fixed effects. OAF decreased blood nonesterified fatty acids and beta hydroxybutyrate concentrations and increased rumination time in early lactation. Leukocytes from IMS cows had lower lactate production and lower glucose consumption after ex-vivo stimulation. OAF did not reduce the acute phase response indicators and reduced the blood concentrations of albumin and antioxidants after calving, suggesting impairment of hepatic functions related to protein synthesis and antioxidant management. Nevertheless, the lack of effect on bilirubin and liver enzymes refutes the possibility of severe liver damage occurring with OAF supplementation. Positive effects in reducing mobilization of body fats and ketogenesis and in increasing rumination time after calving suggest OAF effectiveness in preventing metabolic disorders of the transition period.